Redo "Steps towards making dart2js JS AST templates an indepentent library."

pkg/compiler/lib/src/io/source_information.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.source_information;
 
 import '../dart2jslib.dart' show SourceSpan;
 import '../elements/elements.dart' show AstElement;
 import '../scanner/scannerlib.dart' show Token;
 import '../tree/tree.dart' show Node;
+import '../js/js.dart' show JavaScriptNodeSourceInformation;
 import 'code_output.dart';
 import 'source_file.dart';
 
 /// Interface for passing source information, for instance for use in source
 /// maps, through the backend.
-abstract class SourceInformation {
+abstract class SourceInformation extends JavaScriptNodeSourceInformation {
   SourceSpan get sourceSpan;
   void beginMapping(CodeOutput output);
   void endMapping(CodeOutput output);
 }
 
 /// Source information that contains start source position and optionally an
 /// end source position.
 class StartEndSourceInformation implements SourceInformation {
   final SourceFileLocation startPosition;
   final SourceFileLocation endPosition;
@@ skipping 127 matching lines @@
   int get offset => token.charOffset;
 
   String getSourceName() {
     return name;
   }
 
   String toString() {
     return '${super.toString()}:$name';
   }
 }